DESCRIPTION: Lipids covalently modify many proteins involved in membrane- bound signaling systems.In contrast to myristoylation and prenylation, modification by palmitoylation is reversible. The hypothesis to be tested in this proposal is that palmitoylation is a mechanism for regulating protein activity. To test this hypothesis, the heterotrimeric G proteins will be used as a model system to study how palmitate attachment regulates protein activity. The following specific aims are proposed: 1) purification of palmitoylated and non- palmitoylated G protein alpha subunits; 2) comparison of palmitoylated and non-palmitoylated proteins in various assays of G protein activity; 3) purification and characterization of the palmitoyltransferase that catalyzes the covalent attachment of palmitate to these proteins; and 4) isolation of a cDNA clone encoding the palmitoyltransferase.